1. Field of the Invention
The present invention is directed to an apparatus for converting an optical wave having a relatively smaller cross section into an optical wave having a relatively larger cross section.
2. Description of the Prior Art
Coupling optical semiconductor components to monomode optical fibers produces inefficiencies. The different optical spot sizes, wave forms, and modes conducted in the components and fibers make it necessary to match the different spot sizes shapes and modes, alternatively known as cross sections of the optical waves, to one another in order to achieve high coupling efficiencies.
This matching, for example, can ensue with an arrangement of microlenses. However, this approach requires, at a minimum, an involved precision adjustment.
An integrated-optical apparatus of the species initially cited is disclosed in European Application 0 495 292. The mode conversion is already implemented in a semiconductor chip. The monomode fiber can be coupled to the semiconductor chip by simple butt coupling in low-loss fashion and with high adjustment tolerances.
The known integrated-optical apparatus is well-suited for integration with an over-grown waveguide structure having a small spot width of the guided, optical wave. A complicated manufacturing process is required having a plurality of epitaxial steps. The rib waveguides employed in optical switches, for example, are disclosed in European Application 0 415 225 and German OS 40 30 756.